My chassis manual states that the piston pin to connecting rod assembly should be a 'press fit', but I'm not exactly getting at currently - my current piston heads need replacing with some .040 OS heads, and I'm having to pound the old piston pins with a hammer to even move them a bit, heat/cold or not. Is it normal for them to be this tight, or should I do something to the rods before assembling the new pistons? Thanks.

 

you need to take them to a machine shop. you have to have the right holders and a rod heater. if you are pounding on them you may have already damaged the rod but let a engine machine shop handle it. it is NOT a do it yourself project.

 

Affirmative. :P

 

Have YOU "heated" the rods already? If so, let the machine know this, so they can check the rods THOROUGHLY.

Too much heat can change the metallurgy, possibly weakening the rod.

 

We're talking ~550 degrees C, not an open flame or enough to cause a colorchange.

 

They are press fit, as in tons of pressure. The rod end gets heated and then pressure is applied to fit them or remove them. Don't pound on them

 

It is standard procedure to use a press to remove the old pistons, then heat the rod and use a fixture to install the new pistons.

 

550 degrees F, no problem. 550 C might weaken the rod. Aluminum melts at 660 C for example.

 

Well, the heating gun thing said 550 C. I could still hold it with a welding glove, and the pistons were nowhere CLOSE to melting. But, machine shop time.

 

550°C is over 1,000°F, and is when things just begin to glow red hot.

I doubt you got it to 550°C with a heat gun, and you would definitely not have been able to hold it at that temperature without burning the glove.

- Eric

 

I just read the label on the heat gun, nothing more concrete than that. Quite possible that it refers to the temperature of the internal parts, which do indeed glow red hot.